Initiates processing of the request. This method does not have to submit
a response immediately. It can defer transmission of the HTTP response
back to the client without blocking the I/O thread by delegating the
process of handling the HTTP request to a worker thread. The worker
thread in its turn can use the instance of NHttpResponseTrigger
passed as a parameter to submit a response as at a later point of time
once content of the response becomes available.